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To characterize the mechanisms determining tissue-specific ceruloplasmin gene expression during development, the rat ceruloplasmin gene was isolated in a series of overlapping phage clones. The 5'-flanking region was characterized and the transcription initiation site was identified by primer extension and RNase protection. Nucleotide sequence analysis of this region revealed a typical eukaryotic promotor structure, but no obvious homology with cis-acting elements previously characterized as determining tissue-specific gene expression. Transient expression of chimeric ceruloplasmin-reporter gene constructs containing up to 5200 base pairs (bp) of the 5'-flanking region revealed that sequences 732 bp upstream of the start nucleotide were sufficient to confer hepatocyte-specific expression. The region from -393 to -348 was determined by deletion analysis to contain a positive-acting element, and includes sequence partially homologous to the rat albumin D site. Mobility shift analysis revealed that this region specifically binds a heat-labile nuclear protein from rat liver and from newborn but not adult rat lung. Binding to this region was competed by oligonucleotides corresponding to the albumin D site, but not by oligonucleotides corresponding to binding sites for the hepatocyte transcription factors HNF-1, HNF-3, HNF-4, and C/EBP. These data indicate that ceruloplasmin gene expression is determined in part by a cis-acting region 393 bp upstream of the transcription start site, which binds a previously uncharacterized nuclear protein. The tissue distribution of this nuclear protein suggests that it plays a role in directing ceruloplasmin gene expression in lung and liver during development.

cDNA clones corresponding to rat ceruloplasmin were isolated from newborn rat lung and liver cDNA libraries and the nucleotide sequence was obtained. The derived amino acid sequence of rat ceruloplasmin is 93% homologous to the corresponding human sequence and contains a 19-amino acid leader peptide plus 1040 amino acids of mature protein. Southern blot analysis indicates that the ceruloplasmin gene exists as a single copy in the rat haploid genome. Using these cDNA clones in RNA blot analysis, a single 3.7-kilobase ceruloplasmin-specific transcript is detected in fetal rat liver and lung by day 15 of gestation. During fetal development the abundance of this transcript increases selectively in these two tissues and at birth is 60% of that found in the adult liver. Postnatally the temporal pattern of ceruloplasmin gene expression in lung and liver differs. Within the first 3 weeks postpartum ceruloplasmin mRNA content decreases in lung to undetectable levels, while that in the liver reaches adult levels. Primer extension reveals a single identical start site of ceruloplasmin gene transcription in lung and liver and biosynthetic studies indicate that each tissue synthesizes a ceruloplasmin protein which is qualitatively similar to that synthesized by adult liver. Ceruloplasmin mRNA is also detected in human fetal lung explant and a human lung adenocarcinoma cell line suggesting that a similar pattern of expression occurs in the developing human lung. These data indicate that lung is the predominant extrahepatic site of ceruloplasmin gene expression during fetal development and suggest that this protein may play a previously unappreciated role in lung development or pulmonary antioxidant defense.

Mixed sequence oligonucleotides were used to isolate a series of acute-phase human liver cDNA clones corresponding to the serum alpha 2-globulin ceruloplasmin. These clones were characterized, sequenced, and used to analyze changes in hepatic ceruloplasmin mRNA content during inflammation. In all species examined, hepatic ceruloplasmin mRNA content increased approximately 6-10-fold over control values within 24 h following the induction of inflammation. The mechanisms leading to this increase in hepatic ceruloplasmin mRNA content were studied following turpentine-induced inflammation in Syrian hamsters. Nuclear run-on assays demonstrated an increase in the relative rate of transcription of the ceruloplasmin gene within 3 h following induction, reaching maximum values by 18 h. Hepatic ceruloplasmin mRNA content increased 2-fold within 12 h following induction, reached maximum values by 24 h, and returned to control within 72 h. In contrast, serum ceruloplasmin concentration did not increase until 36 h, reached maximal levels by 120 h, and remained elevated for the course of the study. These data indicate that inflammation leads to a rapid increase in hepatic ceruloplasmin mRNA content. This increase is largely the result of increased ceruloplasmin gene transcription, but comparison of the relative rate of transcription and mRNA accumulation suggests that changes in ceruloplasmin mRNA turnover are also involved. In addition, translational and/or post-translational mechanisms must account for the observed changes in serum ceruloplasmin concentration seen during inflammation.